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On November 19, local time, the National Science Foundation (National Science Foundation, NSF) announced that it was located 305 meters from Puerto Rico in the Caribbean The single-aperture radio telescope Arecibo (Arecibo) will be permanently shut down and dismantled.

In August and November of this year, the two key supporting steel cables of the Arecibo telescope broke one after another. The damage caused could no longer ensure the safety of the repair operation, nor could it guarantee the safety of the scholars working in the observatory.

As the superior department of Arecibo, NSF stated that it will develop a plan for the dismantling of the telescope in the next few weeks, which may include the use of blasting technology to dismantle the instrument platform suspended on its giant main reflecting surface.

Picture source: JidoBG

Fatal blow

Before the completion of the 500-meter spherical radio telescope in China (FAST), 305The meter-caliber Arecibo is the world’s largest single-aperture radio telescope. It was built in 1963, using the large bowl-shaped pit formed by the limestone in the valley being corroded by flowing water as the base. The main components include a main reflecting surface with a diameter of 305 meters and a suspended 137 meters above the “cauldron” , An instrument platform weighing approximately 900 tons. Arecibo’s second and third reflecting surfaces, as well as radar transmitters and microwave receivers are placed in this instrument platform, which is mainly supported by a dozen steel cables with a diameter of about 8 cm erected by three surrounding pylons.

The instrument platform of the Arecibo Telescope. Image credit: Mario Roberto Durán Ortiz

On August 10, 2020, one of the supporting steel cables slipped from the jack of the pylon, smashing a 30-meter-long gap from the edge of the main reflecting surface below, and the normal operation of Arecibo was suspended.

NSF released news that after the first accident, the Arecibo Observatory and its operator, the University of Central Florida (University of Central Florida)< /span> began to repair, and said that more than 10 million US dollars of funding support was needed for the first stage alone. In addition, the accident investigation also found that nearly half of the telescope supporting steel cables showed signs of slippage. While engineers were studying how to repair the damage and assess the integrity of the overall structure, on November 6, another supporting steel cable broke and the central part of the “cauldron” was also damaged.

The second accident completely broke Arecibo’s repair plan. In subsequent investigations, technicians found that the stress on the steel cable during the accident was only 60% of its expected minimum breaking strength. This shows that the strength of other steel cables may also be lower than expected. Further investigation revealed that new cable break marks appeared on multiple main supporting steel cables.

In the 1990s, Arecibo’s instrument platform had an increase in weight caused by a modification. At that time, some auxiliary steel cable jacks also appeared obviousSlippage. If there is a problem with the steel cable, the 900-ton instrument platform may fall into the main reflecting surface from a height of 137 meters, bringing catastrophic destruction to the Arecibo Observatory.

The third-party engineering company responsible for evaluating the overall structure of Arecibo stated that the overall maintenance of the telescope will be unsafe considering that other steel cables may fail. The company’s engineer Thornton Tomasetti said that strength testing of the remaining support cables could cause the structure to collapse. Based on the results of the above-mentioned technical assessment, NSF decided to shut down the Arecibo telescope and begin planned dismantling to avoid the risk of accidental collapse.

The legend ends

NSF’s decision shocked the astronomy community. Many astronomers, engineers, and other scholars have launched #WhatAreciboMeansToMe on social media to share stories about how Arecibo has affected their careers.

This radio telescope, which has been active for more than half a century, not only helped scientists find the first evidence of the existence of an extrasolar planet in 1992, but also a mysterious signal of the universe-repeated rapid radio bursts.(repeating Fast Radio Burst)‘s first “recorder”. In 1974, the Arecibo Observatory transmitted the world’s first interstellar information to a galaxy 12,000 light years away from the Earth, which also made it a symbol and symbol for exploring alien civilization.

For astronomers studying asteroids, the loss of the Arecibo telescope means the loss of an important research position. Its instrument platform includes a powerful radio transmitter that can gather radio waves into a very small radiation beam and emit it. These radio waves will be reflected back when they hit celestial bodies in the solar system (such as asteroids), but the energy of the echo is very small. Only a radio telescope with a huge caliber and high sensitivity like Arecibo can receive it.

By studying the radio signals reflected by these objects, planetary scientists can obtain information about the planet’s orbit, construct a map of the planet’s surface, and study their composition. thingIn fact, Arecibo has played an important role in NASA’s planetary defense program-their goal is to monitor and dispose of celestial bodies that may threaten the safety of the earth.

The main reflecting surface of the Arecibo telescope. Image credit: Mario Roberto Durán Ortiz

Ralph Gaume, head of NSF’s astronomy department, said that some scientific research projects of the telescope may be transferred to other research facilities, and related scholars should have similar transfer proposals or applications. However, because some equipment groups only operate on the Arecibo telescope, there are also some projects that cannot find spare observation facilities.

Where to go

Before the shutdown, the Arecibo telescope has been receiving regular updates and upgrades. If the two steel cable damage accidents this year did not occur, there would be an extra one worth 5.8 million US dollars on the instrument platform (about 38.12 million yuan)< The /span> antenna can greatly increase the sensitivity of the telescope. Now, the Brigham Young University team in charge of this antenna project said that it will discuss with the NSF where the antenna should go. But they are more worried about the future of the many outstanding scientific, technical, management and support personnel of the Arecibo Observatory than the antenna.

As the main center of science and education in Puerto Rico, the observatory provides professional support for many astronomers and engineers, and is also a famous pop culture mecca. An astronomer from the University of Puerto Rico said in an interview with Nature News that the loss of the Arecibo telescope would cause major losses to science, the planetary defense program, and Puerto Rico.

However, the telescope is not all of the Arecibo Observatory. According to information released by NSF, some small scientific projects can still be carried out in other facilities of the Arecibo Observatory, such as two lidars(LiDAR) facilities will still research atmospheric phenomena by launching lasers into the atmosphere; the University of Central Florida, the operator of the observatory, has cooperated with Microsoft to store and analyze relevant data in the cloud. Data is migrated to unaffected servers. In addition, NSF is also exploring the possibility of using the observatory’s resources for educational purposes.

Arecibo Observatory logo. Picture source: Mutante

The cost of dismantling the Arecibo telescope is currently unclear. Sean Jones, deputy director of the NSF Department of Mathematics and Physical Sciences, said: “We understand how important Arecibo is to the astronomy community and Puerto Rico. This is a difficult decision.”

Main reference materials:

https://www.nsf.gov/news/news_summ.jsp?cntn_id=301674

https://www.nature.com/articles/d41586-020-03270-9

https://www.sciencemag.org/news/2020/11/famed-arecibo-telescope-brink-collapse-will-be-dismantled p>

https://www.linkresearcher.com/information/e4bb7359-c675-47f4-9ad7-86e770554d67